HIV blood screening
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The risk of transmitting HIV infection to blood transfusion recipients has been drastically reduced by improved donor selection and sensitive serologic screening assays in many countries. In 2000, WHO estimated that 1 million new HIV infections around the world resulted from inadequate blood screening.Screening tests require a high degree of confidence that HIV is not present, so a combination of antibody (serology), antigen and nucleic acid based tests are used by blood banks in Western countries. The average window period with antibody tests is 22 days. Antigen testing cuts the window period to approximately 16 days and NAT further reduces this period to 12 days. FDA 2001Public demand in the United States for HIV blood screening arose during the campaign to re elect President Ronald Reagan. In April 1984, U.S. Health and Human Services Secretary Margaret Heckler announced to the world at a press conference that an American scientist, Dr. Robert Gallo, had discovered the probable cause of acquired immune deficiency syndrome AIDS: the retrovirus subsequently named Human Immunodeficiency Virus HIV.The first screening test, an ELISA antibody test, had a high sensitivity but a low specificity. The low specificity of the test is due to cross-reacting antibodies, which attach to HIV particles "by accident", even though the body has never encountered HIV. Antibody tests cannot detect recent HIV infections, because there is a window period of several weeks between infection and the production of antibodies. Antigen and nucleic acid based tests have been introduced in some countries to reduce this window period.
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